1. Field of the Invention
This invention relates generally to conductive studs formed across several functional layers of magnetic recording devices, and more particularly to conductive studs formed with bottom undercut portions which are anchored within surrounding insulative materials.
2. Description of the Related Art
Thin film magnetic heads are primarily used in magnetic storage systems to write/read information in the form of magnetic pulses to/from a relatively moving magnetic medium. A magnetic transducer, such as an inductive or magnetoresistive head (MR or GMR type), is typically formed on a slider which is then mounted to a suspension arm of an actuator. The suspension arm suspends the head in close proximity to a disk surface.
Head supporting sliders are generally fabricated from a thin wafer of substrate including a matrix of thin film magnetic heads formed on one of the wafer surfaces. A number of known fabrication techniques may be used to form the heads, e.g., sputtering, vapor deposition, photolithography, and plating. The particular processes used will depend on the type of head being constructed, but generally each process includes a stage wherein terminal pads or studs are formed at the slider's trailing edge for providing an electrical contact to the functional head element. For example, the formation of an inductive head can be separated into four stages: the construction of the first magnetic pole; formation of the conductor coil; construction of the second magnetic pole; and formation of the electrical conductors (studs). Four terminal pads or studs are usually required for each head. Upon completion of the studs, wafers are sliced and diced by known methods to form individual sliders. The sliders are then bonded to suspension arms, and leads from the suspension are soldered to the studs. Relatively large conductors are used in thin film heads to provide desired characteristics of mechanical stability, chemical stability and low contact resistivity.
Depending on the shape of the stud, it may have an undesirable tendency to break away from its surrounding materials. To illustrate, FIG. 1 is a cross-sectional view of a conventional interconnection structure 200 of a magnetic recording device. A conductive stud 220 includes a top stud portion 202 made of gold (Au) and a bottom stud portion 206 made of copper (Cu). In the cross-sectional view, top stud portion 202 has a generally rectangular shape and bottom stud portion 206 has a generally trapezoidal shape with its shorter base side formed over conductive layer 204 (on top of seed layer 208). Bottom stud portion 206 is formed over and coupled to a full conductive layer 204 made of copper (Cu), typically through a thin conductive seed layer 208. Conductive layer 204 is also coupled to either the read head element or the write head element of the magnetic head. An insulator 210 is formed around bottom stud portion 206 over conductive layer 204, such that a top planarized surface is formed with the top of bottom stud portion 206. Top stud portion 202 is formed to make contact with and cover the top of bottom stud portion 206 and has edges which extend over top portions of insulator 210. A lead (not shown) is typically connected to top stud portion 202.
A more simplified cross-sectional view of this interconnection structure is shown in FIG. 2. FIG. 2 shows a conventional trapezoidal stud 304 formed within surrounding materials 302 (e.g. an insulator) with its top generally exposed. A conventional process of making trapezoidal stud 304 involves etching a hole into surrounding materials 302 and forming the stud 304 within the hole. Unfortunately, the etch process is relatively unstable in forming a suitable shape and size for stud 304. As illustrated in FIG. 3, such a trapezoidal stud 304 has a tendency to physically break away from these surrounding materials 302 due to the segregation effect along the borderline. This is highly undesirable, as conductive studs should be securely attached to provide for a reliable electrical coupling within the magnetic recording device.
Accordingly, what are needed are improved interconnection structures and conductive studs for magnetic recording devices and methods of making the same.